Figure 1. Functional characterization of BbFPN.

(a–d) BbFPN-mediated transport of (a) Fe²⁺, (b) Co²⁺, (c) Mn²⁺ and (d) Ni²⁺. Time-dependent quenching of calcein fluorescence inside the liposomes is shown. Addition of transition-metal cation and the ionophore calcimycin (Cal) is shown above the graphs. (e–g) The transport activity of BbFPN measured with (e) the presence (+) or absence (−) of the ionophore gramicidin, (f) the pH gradient across the membrane, or (g) the different pH of the buffer solution. In e–g the pH of the buffer solution is pH 7.0 unless otherwise stated in the boxes. The control data of empty liposomes were measured at pH 7.0. All measurements were repeated three times, and representative data are shown.